[pure-silver] Re: D-Max with pyro


----- Original Message ----- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Monday, December 12, 2005 11:00 AM
Subject: [pure-silver] Re: D-Max with pyro


I have found that a wash
with Sodium Metaborate makes a big difference

Others claim that an alkaline rinse like metaborate does nothing more
than increase the overall stain and contributes nothing to the image.
Since this stain is not formed during image formation I would tend to
agree with this comment.

I have begun to question my understanding of the nature of the pigment produced by Pyro stain developers. I know it is a pigment and not a dye and that the pigment is very permenant, but I am not at all certain of its reaction to pH. Dyes are well known to react to changes in pH, which can decolorize some of them but I thought that the Pyro stain was immune to this. My undertanding is also that it can't _wash_ out. The stain image _can_ be removed by a Peroxide bleach but this is pretty far from anything which happens in normal processing.
The use of after treatment using deveveloper, claimed to intensify the stain, evidently only adds overall stain, the equivalent of fog, which is undesirable.
The stain is a result of the reaction products of the developer. It is certainly variable with the formulation of the developer, for instance, large amounts of sulfite can eliminate it and there are formulas in the literature for non-staining Pyro developers. However, once formed the pigment seems to be quite permanent. I wonder if Ryuji has any thoughts on this.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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